1. Field of the Invention
The present invention generally relates to an apparatus for detecting neural activity and, more specifically, for detecting neural activity for the purpose of control of an external device.
2. Description of the Related Art
Muscle paralysis affects over one hundred thousand people in the United States and approximately one million people worldwide. One approach used to provide assistance to paralyzed people has been described by the U.S. Pat. No. 4,852,573, which is hereby incorporated by reference.
One class of patients who face severe difficulties in their daily lives is those with locked-in syndrome. Locked-in syndrome patients generally have a cognitively intact brain and a completely paralyzed body. They are alert but cannot move or talk. They face a life-long challenge to communicate. Some patients may use eye movements, blinks or remnants of muscle movements to indicate binary signals, such as “yes” or “no.” To enhance communication with these patients, several devices have been developed including electroencephalographic (EEG) control of a computer. These systems can provide patients with the ability to spell words.
One approach is to implant the neocortex using a neurotrophic electrode that uses trophic factors to encourage growth of neural tissue into a hollow electrode tip that contains two wires. The neural tissue is held firmly within the tip because it grows through both ends and joins with neighboring neuropil. This has provided stable long-term recordings in rats and monkeys for up to sixteen months. The histological analysis in rats and monkeys shows normal neuropil without neurons but with an abundance of myelinated axons. Similar implantation on human patients have shown that stable brain signals can be recorded and the patients can control these signals and to use them to drive a cursor on a computer screen.
The above approach requires an intrusive insertion of neurotrophic electrodes inside of the cortex, which requires risky and delicate surgery. Thus, there is a need for a system and method that enable capturing of neural signals without an extensive and intrusive insertion of neurotrophic electrodes.